Relationship between regional F-18-fluorodeoxyglucose and N-13 ammonia uptake in normal myocardium assessed by positron emission tomography: Patternsof mismatch and effects of aging

Increased regional myocardial F-18 fluorodeoxyglucose ((18)FDG) uptake in r elation to N-13 ammonia ((NH3)-N-13) uptake - i.e. glucose metabolism-blood flow 'mismatch' - appears to be a strong indicator of myocardial viability in patients with ischemic heart disease (IHD) and regionally reduced contr actile function. Reference values of regional (18)FDG and (NH3)-N-13 uptake have not been determined in healthy subjects with the target age for the d evelopment of IHD. We therefore studied healthy middle-aged and old men usi ng positron emission tomography (PET). Twenty-three healthy men aged 51 to 83 years of age were studied. (18)FDG and (NH3)-N-13 uptake was quantified in 16 myocardial segments with PET and circumferential profile analysis. Th e relative (18)FDG/(NH3)-N-13 uptake was considerably heterogeneous with (1 8)FDG uptake consistently higher than (NH3)-N-13 uptake in the left lateral ventricular wall. This regional 'mismatch' pattern was observed in all sub jects, but was most prominent in middle-aged men. The observed age-dependen cy was the result of a progressive increased in (NH3)-N-13 uptake with adva ncing age in the left ventricular lateral wall. Age-matched reference value s of myocardial (18)FDG and (NH3)-N-13 uptake appears to be important for t he discrimination between physiological and pathological glucose metabolism -blood flow mismatch assessed by PET and circumferential profile analysis.